The present application is generally directed to a snap hinge, particularly to a hinge usable in injection molded one-piece plastic closures.
The dispensing of consumable materials such as cosmetics and food stuffs creates a demand for dispensing closures which can be manufactured economically and which fully seal the container when in the closed position. Because such closures are often utilized in disposable containers for consumer goods, the cost of such closures is of substantial concern, as is the desire for closures which have excellent consumer convenience and a good tactile feel.
In the past, a first class of closures employing a single main hinge connection or a plurality of main hinges aligned along a single axis were often used. Some of these hinges employ an intermediate element such as a spring element or a taut band in order to produce a dead center position where tension within the closure will prevent the closure from stably resting in its position, driving the closure either more fully open, or more fully closed. Such an unstable equilibrium position is generally thought desirable in closures of this type as it provides the consumer with a closure with a generally good tactile feel. However, such single main hinge type closures, even provided with such an intermediate element, require significant offset of the main hinge from the closure contour due to the simple movement of the cap as illustrated in FIG. 3 of the present application. These hinges are also difficult to mold due to asymmetrical flow paths during molding. This therefore places the hinge well outside the closure body, considered undesirable in such closures. Such single main hinge type closures are also often difficult to mold. An example of such devices employing a single main hinge include those disclosed by U.S. Pat. No. 4,403,712 to Weisinger and U.S. Pat. No. 4,638,916 to Beck et al.
A second class of hinges employs a multiple joint axis hinge arrangement. However, the opening and closing of the multiple joints is uncoordinated in this class of hinges. An example of such an uncoordinated hinge is U.S. Pat. No. 5,148,912 to Nozawa where two hinge parts are connected to each other via two resilient belts which are flexible or elastic over their entire length. In such a closure, the resilient belt plates connecting the hinged lid to the body bend or flex over their entire length in order to produce a force driving the hinge into a single stable position, the hinge otherwise being continually stressed. A lack of coordination between the multiple axis of the hinge allows the lid to move in multiple paths with respect to the closure, there being no coordination between the closure parts.
A third class of hinges are coordinated multi-axis hinge arrangements which generally pivot about two hinge axes and are designed with two, typically tensionless, stable positions, namely a dead center or unstable equilibrium position being provided therebetween. In such a hinge, an over centering force tends to drive the hinge to one of two stable positions from the dead center position. Such hinges are believed to be the invention of an inventor of the present application and are best described in U.S. Pat. No. 5,794,308 entitled xe2x80x9cHingexe2x80x9d. Although at the time the ""308 invention was invented, the model of FIG. 1 of the present invention was not known, the invention of the ""308 patent can generally be described with reference to this model. Such hinges employ a pair of hinge elements including a flexurally rigid intermediate hinge part 4 coupled to the first and second hinge parts, typically the body and lid of a closure via coupling elements 6, 7 which provide elastic relieving movement in the region of a dead center position.
In other words, in the ""308 patent, coupling elements which are connected directly to the substantially flexurally rigid intermediate hinge part, absorb elastic deformation to produce the snap action forces in the region of the dead center position. While the teachings of the ""308 patent provide an excellent closure, since the time of the invention of this patent, the inventors of the present application have discovered various ways to vary and enhance the performance of hinges of the type discussed in the ""308 patent.
It is accordingly an object of the present invention to improve upon the design of the aforementioned hinges by, at least in part, transferring the forces of distortion or deformation created by the flexurally or torsionally rigid intermediate parts or connecting arms to one or more resilient areas facilitating storage of this energy remotely from the coupling elements or areas to which the flexurally rigid connecting arms are connected.
It is a further object of the present application to increase the capacity of a closure to absorb resilient energy from torsionally stiff connecting arms, by transferring some or all of that energy to areas not directly adjacent from the bending areas to which the connecting arms are connected, thereby improving the resilient snap-action force obtained from a particular closure geometry, particularly in closures of relatively small size.
According to the concepts of the present application, the first and second hinge parts are connected by at least two connecting arms separated from each other and connected to the hinge parts by bending regions. The connecting arms are substantially torsionally stiff and the connecting arms, when the closure is moved from one stable state to the other, impart resilient forces to one or both of the first and second hinge parts. These forces are then transferred by coupling or transmitting areas to one or more resilient storage areas which store the deformation forces as spring energy due to bending. Although these coupling or transmitting areas may be themselves resilient and store energy as contemplated by the ""308 patent, the inventive embodiments of the present application transfer some or all of this energy to resilient areas remote from the bending areas.
According to further teachings of the present application, the offset of the hinge from the parting line between the body and lid of the closure may be varied in order to accomplish desired effects such as, in one embodiment, providing a latching mechanism, and in another embodiment, avoiding interference between the lid and body during closure, even in the presence of protrusions from the closure body or unusual shapes designed into the closure lid.
According to further teachings of the present application, the molds used to produce such a coordinated multi-axis hinge arrangement may be designed to compensate for mold shrinkage in the body, lid and connecting arms and still produce desired geometries. Optimal thin film hinges operate as efficient bending areas for the hinge.
The accomplishment of the objectives of the present application will become more fully apparent from the detailed description given hereafter from which the spirit and scope of the invention will become apparent to those skilled in the art. It should be understood, however, that the specific examples and description presented herein below are merely exemplary of the present invention which is described solely by the appended claims.